As is well known, a brace can perform a purely prophylactic function, or provide an assistive force that helps the user to extend their limb, or both. Knee braces in particular can provide physical protection against injury, and may for example be used by athletes involved in high-risk sports where there is a relatively high susceptibility to sustaining a knee injury.
Many individuals suffer from knee problems, often due to a prior knee injury. Some such problems can significantly affect mobility and/or the ability to support the injured person. While corrective measures such as exercise and physiotherapy, or in more serious cases surgery, can assist in correcting or partially alleviating some knee problems, there remains a need in many cases for knee support and extension augmentation.
Particularly where there has been ligament damage, for example a tear or strain in the anterior cruciate ligament (ACL), medial collateral ligament (MCL) or lateral collateral ligament (LCL), a knee brace can be used to both provide support and enhance extension strength, and thus reduce the load on the injured knee. Conventional knee braces that provide active assistance to knee extension are designed to yield when the knee is flexed, loading a torsion spring or compression spring in the process. The spring is loaded when the user bends their leg, and when extending their leg the spring unloads applying a force that augments the extension action. This also helps to support the user and prevent collapse if the injured knee buckles.
A substantial force is required to significantly enhance knee extension and resist buckling of the knee. An example of a knee brace capable of providing the required force is described and illustrated in U.S. patent application Ser. No. 14/526,826 filed Oct. 29, 2014 entitled BRACE AND TENSION SPRINGS FOR A BRACE, which is incorporated herein by reference and referenced by way of non-limiting example only. This brace design provides effective enhancement of the knee extension action in cases where strength enhancement is needed and resistance to buckling of the knee.
However, the forces imparted by the springs in the aforesaid brace create problems with maintaining the correct position of the brace in use. The brace has substantially rigid upper and lower frames which articulate about a joint, typically a polycentric hinge. The upper and lower frames are in turn secured to the leg above and below the knee, respectively, often by straps secured around the leg. Since the ankle cannot be used to support the brace because this would inhibit use of the foot, in a conventional knee brace the strap securing the lower frame to the user's leg is typically secured above the calf (since below the calf the leg tapers in a downward direction). However, because of the large forces involved, even where a strap is secured above the calf over repeated cycles the brace will tend to migrate down the user's leg. This problem is exacerbated by the fact that the cross-sectional shape of the leg changes slightly as the leg moves
It would accordingly be advantageous to provide a stabilizing system for a brace that stabilizes the brace in a set position over repeated extension cycles.